1. Wash and hull the strawberries, then cut each in quarters.
2. Wash peaches. To peel, dunk them into boiling water, leave for 30 seconds to one minute, then immediately plunge into ice water.
3. When peaches are cool enough to handle, remove the skin.
4. Cut peaches in half and remove pit, then slice the fruit.
5. Place the strawberries and peaches into a large pot.
6. Stir in the lemon juice and pectin.
7. Heat the fruit over medium heat until it begins to soften (about 10 minutes).
8. Mash the softened fruit and add the sugars.
9. Bring the mixture to a boil and let it continue to cook until thick (about 25-30 minutes) or until it reaches 221F on a candy thermometer.
10. Watch your jam carefully to prevent scorching, stirring often.
11. If you're worried or think you can smell the mixture starting to burn, turn the heat down and cook slowly until the jam tests done.
12. Testing can be done by dipping a spoonful of the hot jam onto a china or glass plate that has been kept in the freezer.
13. Give the jam on the plate a moment or so to cool and then see if it's gelling to your satisfaction.
14. When the jam is ready, stir in the cinnamon and remove the pot from the heat.
15. Let sit for 5 minutes, then skim off all the foam.
16. Ladle the jam into hot sterilized jars, leaving 1/2 inch headroom.
17. Wipe the rims clean, place lids and adjust the rings fingertip tight.
18. Process in a hot water bath for 5 minutes.
19. Cool completely, check seals and label.
20. Store in a cool, dry, dark place for up to 1 year.